"So far. we have seen 39 development cycles of Linux 2.6 and the 40th is about to start. However, Linux 2.6.39 might be the end of the Linux 2.6 series. In an email, Linus Torvalds wrote that the numbers are becoming too big and he might [be] thinking of giving the next release a version number of 2.8.0. [...] In the ensuing discussion, Torvalds wrote that a version number of 3.0 is also a strong possibility", as a natural way to introduce a new numbering scheme where odd numbers are also used for stable releases and feature releases increment the second digit.

Nowadays everyone is doing version numbers close or above 10 and cool ones have an animal name to further confuse people.

To make things easy, Linus should use a year.month.update scheme so he doesn't have to worry about when to bump the major/minor versions. As long as he doesn't release two kernels in the same month then this will work.